Tried to make lined shading go with the contours at first, but it didn’t work on this object. Generally a little tricky to do as each line must gradually change contour.
Then a drawing of a pear:
An attempt to shade it using only black and mid-grey:
This wasn’t a success because it’s difficult to give a sense of form with only two shades. Probably works okay with angular forms, but not so much organic forms. Need to introduce an extra shade.